A couple of percent diff in drivetrain efficiency is going to make almost no difference to riding speed. You have to recalculate the difference in total drag, and the drivetrain drag is only a small proportion of the total. Imagine you're riding a road bike at about 16mph. That takes about 150Watts. Most of the 150Watts is consumed fighting the air. Some on rolling resistance. A few watts are lost to the drivechain, say its 10W (I'd be surprised if it's this high). 4% of 10W = 0.4W, so a 4% difference in drivetrain efficiency is only going use up 0.4W of your power. Negligible.
(I made up the figures, so actual ones will be different. Point still stands, 'tho)